Afghan soldiers stand guard outside an airport gate in Kabul, after a shooting incident in Kabul, Afghanistan, on Wednesday, April 27. An Afghan Army officer opened fire on foreign troops Wednesday after an argument at the airport in the capital, the latest in a spate of deadly incidents that have occurred inside government or military installations, the Defense Ministry said.

Kabul — An Afghan Air Force officer murdered eight foreign soldiers from NATO and one foreign contractor on the military side of the Kabul airport on Wednesday afternoon.

The attack in the heart of Kabul and in a heavily guarded based filled with soldiers from the US and other NATO allies is bound to raise questions about the US-led war effort, following a brazen escape of hundreds Taliban prisoners in Kandahar earlier this week and growing signs that average Afghans are chafing against a foreign military presence that's almost 10 years old.

The US relationship with Afghan President Hamid Karzai, who America helped install in power, is rocky and there are indications that Afghan security forces, slated to take control of some parts of this country this summer, are not prepared.

On Monday, the oversight body for US spending in Afghanistan said the Afghan ministry of interior doesn't know how many police are in its employ and that there are indications that the ministry pays salaries to Afghans who don't work. The international community has spent about $1.3 billion on the Afghan National Police since 2002.

The murders today point to the most crucial question about the war in Afghanistan, as the summer fighting season fast approaches: Are enough Afghan soldiers and police prepared and sufficiently loyal to make the US vision for Afghanistan a reality? This summer is already shaping up to be unusually violent.

Sami Kovanen from Indicium Consulting says insurgent attacks are up about 80 percent this spring compared with last spring, and that at the moment there are over 400 insurgent attacks a week throughout Afghanistan.

Taliban claim

Ministry of Defense officials say the shooting stemmed from a personal disagreement. The Taliban say the killer worked for them.

The shooting comes on the heels of a prison break earlier this week that saw nearly 500 insurgents tunnel out of Kandahar’s central prison. The complexity of that escape and the recent wave of killings inside secure bases casts doubt on NATO’s claims of steady progress in Afghanistan.

Today's killings mark the fourth time this month a member of the Afghan security forces, or someone dressed in an Afghan security uniform, killed soldiers inside a secure military compound. Despite the recent uptick of attacks carried out by people in Afghan military uniforms, NATO officials say they do not have a problem with insurgent infiltration inside the Afghan security forces.

Not including the last three incidents, US Air Force Ltc. Dave Simons says there have been 16 incidents of people dressed in Afghan security forces uniforms turning their weapons against their fellow soldiers or NATO forces since 2009

“About half of the incidents that we track have resulted from an argument or a guy that’s just gone off the deep end so to speak,” says Colonel Simons, a public affairs officer for the NATO training mission in Afghanistan. “The reality of it is that we still look at the Afghan soldiers, air force, and police as our friends. Our mission here is to train them and that’s what we plan on doing.”

Military and police uniforms are on sale in markets throughout Afghanistan. Last week, the Ministry of Interior declared it illegal to resell military and police uniforms and confiscated many from shops.

Still, there is much concern that Afghanistan as insurgents have demonstrated their ability to carry out increasingly complex operations, though in rural areas in the south of Afghanistan, there are reports that Taliban have lost some mobility due to the increased Afghan and foreign troop presence.

“The Taliban cannot conduct their operations in the southern rural parts of the country, so they’re mostly now concentrating on the urban areas and trying to penetrate the government,” says Khalid Pashtoon, a member of the Afghan Parliament from Kandahar. “They are trying to show that they’re not defeated... but, actually, they’re getting weak.”